{"id":126801,"date":"2022-07-25T14:05:59","date_gmt":"2022-07-25T14:05:59","guid":{"rendered":"https:\/\/blog.finxter.com\/?p=510694"},"modified":"2022-07-25T14:05:59","modified_gmt":"2022-07-25T14:05:59","slug":"how-to-convert-a-list-of-objects-to-a-csv-file-in-python-5-ways","status":"publish","type":"post","link":"https:\/\/sickgaming.net\/blog\/2022\/07\/25\/how-to-convert-a-list-of-objects-to-a-csv-file-in-python-5-ways\/","title":{"rendered":"How to Convert a List of Objects to a CSV File in Python [5 Ways]"},"content":{"rendered":"\n
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5\/5 – (1 vote) <\/div>\n<\/div>\n

\"\ud83d\udcac\" Question<\/strong>: How to convert a list of custom objects to a csv<\/code> file? <\/p>\n

Example<\/strong>: Given is a list of custom objects of, say, type Employee<\/code> that holds the name, job description, and income like so:<\/p>\n

salary = [Employee('Alice', 'Data Scientist', 122000), Employee('Bob', 'Engineer', 77000), Employee('Ann', 'Manager', 119000)]<\/pre>\n
Your goal is to write the content of the list of objects into a comma-separated-values<\/a> (CSV) file format. <\/p>\n
Your output file should look like this:<\/p>\n
# my_file.csv<\/em><\/strong>\nAlice,Data Scientist,122000\nBob,Engineer,77000\nAnn,Manager,119000<\/code><\/pre>\n
Solution: <\/strong>There are four simple ways to convert a list<\/a> of lists to a CSV file in Python<\/a>.<\/p>\n
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  1. CSV<\/strong>: Import the csv<\/code> module<\/a> in Python, create a csv writer object, and find a list lst<\/code> of elements representing each object as a row, that is then written into the CSV using writer.writerow(lst)<\/code>.<\/li>\n
  2. Pandas<\/strong>: Import the pandas library<\/a>, convert each object to a list to obtain a list of lists, create a Pandas DataFrame out of the list of lists, and write the DataFrame to a file using the DataFrame method DataFrame.to_csv('file.csv')<\/code>.<\/li>\n
  3. NumPy<\/strong>: Import the NumPy library<\/a>, convert each object to a list to obtain a list of lists, create a NumPy array, and write the output to a CSV file using the numpy.savetxt('file.csv', array, delimiter=',')<\/code> method.<\/li>\n
  4. Python<\/strong>: Use a pure Python<\/a> implementation that doesn’t require any library by using the Python file I\/O functionality.<\/li>\n<\/ol>\n
    \"\u2b50\" Finxter Favorite<\/strong>: My preference is Method 4 (Vanilla Python<\/strong>) because it’s simplest to use, efficient, and most robust for different input types (numerical or textual) and doesn’t require external dependencies and data wrangling.<\/p>\n
    Method 1: Python’s CSV Module<\/h2>\n
    You can convert a list of lists to a CSV file in Python easily—by using the csv<\/code><\/a> library. This is the most customizable of all four methods.<\/strong><\/p>\n
    class Employee(object): def __init__(self, name, description, salary): self.name = name self.description = description self.salary = salary employees = [Employee('Alice', 'Data Scientist', 122000), Employee('Bob', 'Engineer', 77000), Employee('Ann', 'Manager', 119000)] # Method 1\nimport csv\nwith open('my_file.csv', 'w', newline='') as f: writer = csv.writer(f) for x in employees: writer.writerow([x.name, x.description, x.salary]) <\/pre>\n
    Output:<\/p>\n
    # my_file.csv<\/em><\/strong>\nAlice,Data Scientist,122000\nBob,Engineer,77000\nAnn,Manager,119000<\/code><\/pre>\n
    In the code, you first open the file using Python’s standard open()<\/a><\/code> command. Now, you can write content to the file object f<\/code>. <\/p>\n
    Next, you pass this file object to the constructor of the CSV writer that implements some additional helper method—and effectively wraps the file object providing you with new CSV-specific functionality such as the writerow()<\/code> method. <\/p>\n
    You now iterate over the objects and convert each object to a list.<\/p>\n
    The list representing one row is then passed in the writerow()<\/code> method of the CSV writer. This takes care of converting the list of objects to a CSV format. <\/p>\n
    You can customize the CSV writer in its constructor (e.g., by modifying the delimiter from a comma ','<\/code> to a whitespace ' '<\/code> character). Have a look at the specification to learn about advanced modifications<\/a>. <\/p>\n
    Method 2: Pandas DataFrame to_csv()<\/h2>\n
    This method converts a list of objects to a CSV file in two steps:<\/p>\n